In 1941, Fr. Germanos was elected Bishop of the titular see of Nyssa. His consecration took place on November 30, 1941 at New York's Archdiocesan Cathedral of the Holy Trinity. The consecrating hierarchs were Abp. Athenagoras, Bp. Athenagoras of Boston, Bp. Eirinaios of San Francisco, Bp. Bohdan of the Ukrainian Orthodox Church in America, and Bp. Sawa of Grodno (Poland). During World War II, Bishop Germanos served as chair of the Greek War Bond Committee.

Following the war, Bishop Germanos was appointed presiding hierarch of the Sixth Archdiocesan District, based in Charlotte, North Carolina. He later returned to New York as editor of the archdiocesan magazine The Orthodox Observer. Upon the death of Archbishop Michael in 1958, Bishop Germanos was designated as locum tenens until the election and enthronement of Archbishop Iakovos the following year.

In 1962, the Holy Synod of the Ecumenical Patriarchate recognized Bishop Gerasimos for his long and dedicated service to the Church in America by electing him titular Metropolitan of Hierapolis. He retired the following year, but continued to serve the Church as he was able.

In ill health for the final years of his life, Metropolitan Germanos died in Astoria on July 13, 1993.